Migrate from Resend

Drop-in API compatibility. Migrate a typical Resend app in under an hour.

API shape compatibility

Mailgrid's POST /api/emails takes the same fields as Resend's POST /emails with a few additions. Your existing call sites should work after only:

Changing the API host: api.resend.com → api.mailgrid.space
Changing the path: /emails → /api/emails
Changing the API key: re_… → mb_live_…

Field-by-field mapping

Resend field	Mailgrid field	Notes
`from`	`from`	Same
`to`	`to`	Same (string or string[])
`cc` / `bcc`	`cc` / `bcc`	Same
`reply_to`	`replyTo`	camelCase
`subject`	`subject`	Same
`html` / `text`	`html` / `text`	Same
`attachments[].path`	—	Inline base64 or fileId only (no URL fetch)
`attachments[].filename` / `content`	Same	`content` base64-encoded
`tags` (array of objects)	`tags` (array of strings)	Simpler shape
`headers`	`headers`	Same

Codemod

A find-and-replace gets you 90% of the way:

sed

# 1. Host + path
sed -i 's|api.resend.com/emails|api.mailgrid.space/api/emails|g' src/**/*.{ts,js}

# 2. Env var
sed -i 's|process.env.RESEND_API_KEY|process.env.MAILGRID_API_KEY|g' src/**/*.{ts,js}

# 3. reply_to → replyTo
sed -i 's|reply_to:|replyTo:|g' src/**/*.{ts,js}

Webhook events

Resend's webhook event names map cleanly:

Resend type	Mailgrid event
`email.sent`	`sent`
`email.delivered`	`delivered`
`email.opened`	`opened`
`email.clicked`	`clicked`
`email.bounced`	`bounced`
`email.complained`	`complained`

What you gain

2.5× cost reduction ($0.40 vs $1.00 per 1k)
MCP server — your agents can drive sends directly
Multi-stream — proper transactional/marketing isolation
File Cache — attach-by-id, dramatic payload reduction
Dedicated IPs at $24.95/mo (Resend: $30/mo)
Self-host option — MIT-licensed, ~$8/mo to run yourself

What's different

No React Email template engine — Mailgrid uses Handlebars (simpler, deterministic). Pre-render React on your side and pass the resulting HTML.
No native dashboard UI yet — API + MCP only.
Attachments don't auto-fetch from URLs — use File Cache or inline base64.